Digital subscriber line, DSL, describes a technology for transmitting high bandwidths information to different subscribers with aggregation of data for multiple subscribers over an optical link layer. A flow control per subscriber is needed from a DSL or G.fast or G.hn transceiver or modem to a passive optical network element, also called PON element hereinafter. By way of example, the fiber uplink may have a capacity of 2.5 Gbps or 10 Gbps (gigabit per second) downstream and 1 Gbps or 10 Gbps upstream data rate while the maximum data rates of the DSL transceiver for a subscriber is limited to 400 Mbps in downstream direction or even 1 Gbps for G.fast transceiver and 100 Mbps in the upstream direction or 1 Gbps for G.fast or G.hn transceiver. Furthermore, different subscribers which are connected to the same physical fiber link may have different data rates. By way of example, a first subscriber connected to the DSL or G.fast or G.hn transceiver can have a subscriber line with 50 Mbps, while another subscriber connected to the same DSL or G.fast or G.hn transceiver may have a 1 Gbps connection. Additionally, the incoming data rate from a central optical line terminal (OLT) accessible via the internet and located at a server providing a service to the subscriber and thus from the PON element connected to the OLT could be much higher such as 2.5 Gbps than the total aggregated data rates of the different subscribers which will be much lower and could also vary from 1 Mbps to 1 Gbps. This corresponds to a situation in which a big pipe of data needs to be throttled to a pipe with smaller dimensions. Hence, a network processor with sufficient memories storage is required for the flow control interface between the DSL transceiver and the PON element. Furthermore, it should be guaranteed that no packets are dropped or a minimum quality of service is guaranteed.
In the following, it is assumed that the DSL transceiver has 16 interfaces or ports to the different subscribers (S0 to S15) for which the data aggregation happens over a single fiber link. If one of the DSL links sees a link drop for Sx the PON device may accumulate packets for this interface or port (Sx). The total memory storage of the PON element gets bloated with the packets from port Sx. Usually, the memory storage is a pool shared for multiple interfaces or ports in the PON element. If the link drops down for one interface out of the 16 interfaces, the memory must not occupy the common pool memory. Otherwise, the services for the other 15 ports or interfaces and the other quality of service (QoS) on those ports could be severely affected. Furthermore, a seamless connectivity between the DSL/G.fast/G.hn transceiver and the PON element, especially the traffic aggregator of the PON element is desirable. However, the data rates of the different individual subscribers handled by the DSL transceiver are not known to the PON element.
Additionally, there is not back pressure mechanism established today between the OLT and the passive optical network (PON) element, which receives data from the OLT and which transmits the data packets to the DSL transceiver.
Accordingly, a need exists to solve the above-mentioned problems and to effectively cope with the situation that different data rates are present for the different subscribers and that the traffic may drop from a high signal flow to no signal at all for one of the subscribers.